Full on-device manipulation of olefin metathesis for precise manufacturing.

Olefin metathesis, as a powerful metal-catalysed carbon-carbon bond-forming method, has achieved considerable progress in recent years. However, the complexity originating from multicomponent interactions has long impeded a complete mechanistic understanding of olefin metathesis, which hampers further optimization of the reaction. Here, we clarify both productive and hidden degenerate pathways of ring-closing metathesis by focusing on one individual catalyst, using a sensitive single-molecule electrical detection platform. In addition to visualizing the full pathway, we found that the conventionally unwanted degenerate pathways have an unexpected constructive coupling effect on the productive pathway, and both types of pathway can be regulated by an external electric field. We then pushed forward this ability to ring-opening metathesis polymerization involving more interactive components. With single-monomer-insertion-event resolution, precise on-device synthesis of a single polymer was achieved by online manipulation of monomer insertion dynamics, intramolecular chain transfer, stereoregularity, degree of polymerization and block copolymerization. These results offer a comprehensive mechanistic understanding of olefin metathesis, exemplifying infinite opportunities for practical precise manufacturing.